Radio frequency (RF) ablation catheters have proven to be a very effective treatment for several cardiac tachyarrhythmias. An example of an RF ablation catheter is described in the brochure entitled Medtronic ATAKR® II Advanced RF Ablation System (2000) available from Medtronic, Inc. Minneapolis, Minn. During an ablation procedure an ablation catheter is introduced into the heart usually via the femoral vein or artery under local anesthesia. A position locating system such as described in the brochure entitled Medtronic Model 9670000 LocaLisa® Intracardiac Navigation System. Certain electrogram characteristics, recorded also via an ablation electrode and additional ring electrodes, allow the physician to locate the area of tachycardia origin and the subsequent energy delivery results in thermal destruction of the arrhythmogenic substrate. The size of the demarcated lesion can be controlled by selecting a certain target temperature and appropriate power limits. The damage of arrhythmogenic substrate is a curative treatment and results in immediate and permanent termination of the arrhythmia making any concomitant palliative treatment such as medication unnecessary.
The clinician typically directly controls power to the ablation catheter by control settings on the RF generator and by an on-off switch operated by the clinician's foot. Clinician direct control of the power delivered to the ablation catheter can be inadequate if the catheter dislocates from the intended ablation position. In some circumstances, ablation catheter dislocation can occur so rapidly that the clinician does not have time to properly respond. Additionally, ablation systems such as the Medtronic ATAKR® II do not provide feedback to the clinician other than ablation catheter tip temperature. Catheter dislocation during RF delivery may result in an unintentional heating of healthy non-arrhythmogenic tissue. For example, catheter ablation to treat Atrial Ventricular Nodal Reentrant Tachycardia (AVNRT) involves an ablation target close to the physiological atrio-ventricular (AV) node, and damage of healthy non-arrhythmogenic tissue in this area can result in complete AV-block and pacemaker dependency. During temperature-controlled ablation, power is continuously adjusted to maintain a preset target temperature. During catheter dislocation electrode temperature will suddenly decrease and as a consequence power will be automatically increased. Increased power to the ablation catheter results in increased electrode temperature that can create a risk to healthy tissue that might come in contact with the electrode.
For the foregoing reasons, there is a need for a medical ablation catheter control that provides increased ablation catheter operation feedback to the clinician and provides the clinician with increased options for programmable control of the ablation catheter.